Solution polymerizations are typically used to form olefin-based polymers. However, such polymerizations are typically capital and energy intensive. There is a need for new olefin polymerization processes that reduce capital requirements, improve energy efficiency, and reduce volatile organic content in the final product. There is also a need for higher molecular weight ethylene-based polymers that have improved processing and improved toughness. Such polymers are needed in sealing applications which require tough, high molecular weight polymers. These polymers typically cannot be prepared using conventional solution polymerization processes, because the polymer viscosity limits the ability to process the polymer.
U.S. Publication No. 2008/0090974 discloses a process to polymerize olefins, comprising contacting propylene, at a temperature of 65° C. to 150° C., and a pressure of 1.72 to 34.5 MPa, with the following: 1) a catalyst system comprising one or more activators, and one or more nonmetallocene metal-centered, heteroaryl ligand catalyst compounds, 2) optionally one or more comonomers selected from ethylene and C4 to C12 olefins, 3) diluent or solvent, and 4) optionally a scavenger. The olefin monomers and any comonomers are present in the polymerization system at 30 weight percent or more, and the propylene is present in the feed at 80 weight percent or more. The polymerization occurs at a temperature above the solid-fluid phase transition temperature of the polymerization system, and at a pressure greater than 1 MPa below the cloud point pressure of the polymerization system, and the polymerization occurs at a temperature below the critical temperature of the polymerization system, or (preferably and) at a pressure below the critical pressure of the polymerization system.
U.S. Pat. No. 4,433,121 discloses a process for polymerizing a monomer under such conditions that the resulting polymer dissolves in the reaction medium. The polymerization is carried out in a polymerization zone at a temperature above the upper cloud point of said polymer solution, and under conditions which enable the polymer solution to be separated into two phases. The polymerization is carried out under stiffing conditions, which maintain the two phases, under said phase-separating conditions, in a dispersed and mixed state. The resulting polymer solution is sent to a separating zone located independently of said polymerization zone, thereby separating it into two phases, a polymer-rich liquid phase that is recovered, and a polymer-lean liquid phase that is recycled to the polymerization zone.
International Publication No. WO 2006/019494 discloses a process to polymerize olefins, comprising contacting, under supercritical conditions, olefin monomers with a catalyst compound, an activator, optional comonomer, and optional hydrocarbon diluent or hydrocarbon solvent. The polymerization takes place in the presence of a fluorinated hydrocarbon.
International Publication No. WO 2004/026923 discloses a process to produce propylene polymers, comprising contacting a metallocene catalyst compound, and an activator, in a reaction medium comprising propylene, from 0 to 30 volume percent of one or more solvents, and from 0 to 30 mole percent of one or more comonomers, under temperature and pressure conditions below the melting point of the propylene polymer. The temperature is at, or above, the critical temperature for the reaction medium, and the pressure is at least 500 kPa above the critical pressure of the reaction medium; or the temperature is 1° C. or more above the critical temperature for the reaction medium, and the pressure is at, or above, the critical pressure of the reaction medium; or the temperature is 1° C. or more above the critical temperature for the reaction medium, and the pressure is at least 500 kPa above the critical pressure of the reaction medium.
U.S. Pat. No. 6,255,410 discloses a process for continuously producing polyolefin comprising: (a) continuously feeding olefinic monomer and catalyst system of metallocene and cocatalyst; (b) continuously polymerizing monomer feed to provide a monomer-polymer mixture; and (c) continuously settling a two phase mixture into a continuous molten polymer phase and a continuous monomer vapor, which may, optionally, be recycled to (a). The monomer-polymer mixture is at a pressure below the cloud point pressure, to provide a polymer-rich phase and a monomer-rich phase, at a temperature above the melting point of the polymer.
International Publication No. WO 2008/076589 discloses a process for polymerizing olefins, comprising the steps of: (a) contacting, in one or more reactors, in a dense fluid homogeneous polymerization system, olefin monomers having three or more carbon atoms present at 30 weight percent or more (based upon the weight of the monomers and comonomers entering the reactor), with the following: 1) one or more catalyst compounds, 2) one or more activators, 3) from 0 to 50 mole percent comonomer (based upon the amount of the monomers and comonomers entering the reactor), and 4) from 0 to 40 weight percent diluent or solvent (based upon the weight of the polymerization system), at a temperature above the crystallization temperature of the polymerization system, and at a pressure no lower than 10 MPa below the cloud point pressure of the polymerization system, and less than 200 MPa. A reactor effluent comprising a polymer-monomer mixture is formed, and is optionally heated, after it exits the reactor, and before or after the pressure is reduced to form a two-phase mixture, comprising a polymer-rich phase and a monomer rich phase.
International Publication No. WO 2004/026921 discloses a process to polymerize olefins, comprising contacting, in a polymerization system, olefins having three or more carbon atoms, with a catalyst compound, activator, optionally comonomer, and optionally diluent or solvent, at a temperature above the cloud point temperature of the polymerization system, and at a pressure no lower than 10 MPa below the cloud point pressure of the polymerization system. The polymerization system comprises any comonomer present, any diluent or solvent present, the polymer product, and the olefins having three or more carbon atoms are present at 40 weight percent or more.
U.S. Pat. No. 5,599,885 discloses the preparation of polyolefin, which comprises polymerizing or copolymerizing olefin in the presence of a catalyst comprising a metallocene compound of a transition metal selected from the Group IVB of the periodic table, and an organoaluminum oxy-compound. The organoaluminum oxy-compound is added to the polymerization system in the form of a slurry, in an aliphatic hydrocarbon or alicyclic hydrocarbon, and the polymerization is carried out in the presence of the aliphatic hydrocarbon diluent or an alicyclic hydrocarbon diluent having a boiling point below 100° C.
U.S. Pat. No. 5,278,272 discloses elastic substantially linear olefin polymers which have very good processability, including processing indices (PI's) less than, or equal to, 70 percent of those of a comparative linear olefin polymer, and a critical shear rate, at onset of surface melt fracture, of at least 50 percent greater, than the critical shear rate, at the onset of surface melt fracture, of a traditional linear olefin polymer, at about the same melt index (I2) and molecular weight distribution. The polymers have higher “low/zero shear viscosity” and lower “high shear viscosity” than comparative linear olefin polymers.
U.S. Pat. No. 6,680,361 discloses shear-thinning ethylene/α-olefin and ethylene/α-olefin/diene interpolymers that do not include a traditional branch-inducing monomer, such as norbornadiene. Such polymers are prepared at an elevated temperature, in an atmosphere that has little, or no, hydrogen, using a constrained geometry complex catalyst and an activating cocatalyst.
International Publication WO 2011/002998 discloses ethylenic polymers comprising low levels of total unsaturation. Compositions using such ethylene polymers, and fabricated articles made from them, are also disclosed.
International Publication WO 2011/002986 discloses ethylene polymers having low levels of long chain branching. Films and film layers made from these polymers have good hot tack strength over a wide range of temperatures, making them good materials for packaging applications.
International Publication WO 2007/136497 discloses a catalyst composition comprising one or more metal complexes of a multifunctional Lewis base ligand, comprising a bulky, planar, aromatic- or substituted aromatic-group. Polymerization processes employing the same, and especially continuous, solution polymerization of one or more α-olefins, at high catalyst efficiencies, are also disclosed.
International Publication WO 2007/136496 discloses metal complexes of polyvalent aryloxyethers, appropriately substituted with sterically bulky substituents. These metal complexes possess enhanced solubility in aliphatic and cycloaliphatic hydrocarbons, and/or when employed as catalyst components for the polymerization of ethylene/α-olefin copolymers, produce products having reduced I10/I2 values.
International Publication WO 2007/136494 discloses a catalyst composition comprising a zirconium complex of a polyvalent aryloxyether, and the use thereof, in a continuous solution polymerization of ethylene, one or more C3-30olefins, and a conjugated or nonconjugated diene, to prepare interpolymers having improved processing properties.
Additional polymerization processes and/or polymers are described in the following references: U.S. Pat. Nos. 3,496,135, 3,502,633, 3726843, 3932371, 4,444,922, 448,195, 4,623,712, 4,857,633, 6,683,153, 7,163,989; U.S. Publication No. 2009/0118466; European Patent Nos. 0149342B1, 0184935B1, 0877834B1, 1339756B1; International Publication Nos. 02/34795, 06/009946, 08/079,565, 11/008,837; Canadian Patent Application Nos. 1203348, 2372121; German Application No. 19905029A1 (machine translation); Japanese Patent Publication No. 58-002307 (Abstract); and Van Vliet et al., The Use of Liquid-Liquid Extraction in the EPDM Solution Polymerization Process, Ind. Eng. Chem. Res., 2001, 40, 4586-4595.
As discussed above, there is a need for new olefin polymerization processes that reduce capital requirements, improve energy efficiency, and reduce volatile organic content in the final product. In addition, the ethylene-based polymers of the art typically have lower molecular weights due to lower viscosities needed to run the polymerizations, and typically contain lower comonomer incorporation, which decreases the toughness of the polymer. As discussed, there remains a need for higher molecular weight ethylene-based polymers that have improved processibility and improved toughness. These needs have been met by the following invention.